Minisymposium 12: Intracellular Signaling

Abs # 24002: Rop GTPase-Regulated Hypoxia Tolerance in Arabidopsis: Genetic and Genomic Analysis of Regulatory and Metabolic Responses

Presenter:	Branco-Price, Cristina
Authors	Branco-Price, Cristina  (A)   Baxter-Burrell, Airica  (A)   Yang, Zhenbiao  (A)   Bailey-Serres, Julia  (A)
Affiliations:	(A): Department of Botany and Plant Sciences, University of California Riverside

Arabidopsis thaliana seedling tolerance of transient low oxygen stress (hypoxia) requires regulated RopGTPase activation of a DPI-sensitive NADPH oxidase that results in hydrogen peroxide production and moderate induction of alcohol dehydrogenase (ADH) mRNA levels and enzymatic activity (Baxter-Burrell et al., 2002, Science 296:2026-28). A Rop GTPase activating protein knockout mutant (ropgap4-1) showed super-induction of ADH and reduced hypoxia tolerance. ROPGAP4 is a negative regulator of Rop signaling; negative-feedback regulation of Rop signaling occurs under hypoxia by Rop-mediated activation of ROPGAP4 expression. DNA microarray (Affymetrix 25K GeneChip) analysis of control and hypoxia-treated seedlings was performed to evaluate: (1) translational regulation, by comparison of the relative abundance of total and polysomal mRNA in WT, and (2) negative regulation of Rop signaling, by comparison of mRNA levels in WT and ropgap4-1. We confirmed that regulation of initiation of mRNA translation is a significant component of the response to hypoxia. Differential regulation of mRNA abundance and translation was evident for genes encoding proteins involved in, (1) carbohydrate consumption and ethanolic fermentation (sucrose synthase, pyruvate decarboxylase, ADH), (2) oxidative stress signaling and reactive oxygen species elimination (NADPH oxidase subunits, superoxide dismutase, glutathione-S-transferase, peroxidase), (3) protein turnover (F-box and SKP), and (4) gene transcription (WRKY, MYB, MADS). Genetic and molecular analyses are underway to confirm and investigate the significance of these Rop-regulated genes/mechanisms in the response to hypoxia. Of particular interest is the regulation of the production and amelioration of reactive oxygen species in the response to hypoxia. Research supported by NSF (MCB-131486) and Portugal’s FCT- Ministério da Ciência e Tecnologia (SFRH/BD/9165/2002).